In general, along with the recent widespread use of data communication networks, home appliances and computers and other peripheral devices are connected via a network even within the home, and the so-called home network, which enables communication between various devices, is becoming more commonplace. A home network enables sharing of data processing functionality of various devices by performing communication between the devices connected to the network. Sending and receiving content between devices connected to the network provides convenience and comfort to the user, and it is expected that hereafter, there will be increased widespread use.
UPnP (a registered trademark) is known as a protocol applicable to the configuration of this type of home network. UPnP can easily construct a network without any complicated operations, and services can be received which are provided by various connected devices which are connected to the network without difficult operations or setups. Also, UPnP has the advantages of not relying on the OS (operating system) of the devices, and of devices being added easily.
UPnP exchanges definition files compliant with XML (extensible Markup Language) between the connected devices, and performs mutual authentication between the devices. An outline of UPnP processing is as follows.    (1) Addressing process to acquire an individual device ID such as an IP address.    (2) Discovery process to perform a search on the network for each device, receive a response from each device, and acquire information such as device type, functionality, and so forth included in the responses.    (3) Service request process to request service from each device, based on the information acquired in the discovery process.
By performing the above-mentioned procedures, services applicable to the devices connected to the network can be provided or received. A device newly connected to the network acquires a device ID from the above-mentioned addressing process, and acquires information about other devices connected to the network in the discovery process, and can request service to other devices based on the acquired information.
For example, in the case of attempting to play back content such as music data or image data stored on the server on a device on the client side, the client acquires information regarding the content retained on the server. The server has content stored in a storage unit and attribute information stored in a storage unit, including information related to various content received externally via the tuner, and provides this information to the client. The attribute information includes, for example, the title of a song or movie, the artist name, recorded date as the content, and other information relating to the data compression state for example. This attribute information is called metadata or meta information.
The client can perform an acquisition request to the server for content attribute information for various content information stored on the server, for example the title of a song or movie, the artist name, and also data compression state information (ATRAC: adaptive transform acoustic coding, MPEG: moving picture experts group, and so forth), and further, copyright information, as necessary.
The server sends to the client the metadata (attribute information) relating to the content retained on the server according to the request by the client. The client displays the content information on a display of a client device according to a predetermined display program based on the metadata acquired from the server. For example, a song title list formed of the artist name and title and so forth, for example, is displayed on a display. The user confirms or selects the content object for playback, based on the display information, and sends a content transmission request to the server. The server receives the content request from the client, and content transmission is performed from the server to the client according to the received request, and playback of the received content on the client side is performed.
Thus, the content stored on the server is searched for from other devices (clients) connected to the network, and specific content can be specified and played back.
Also, a server configuration having a delivery configuration of so-called live streaming data is proposed, wherein a tuner functionality is established on the server which provides the content, the video or audio data received via the tuner is sent to the client. The configuration is such that, for example, various types of broadcasting data such as terrestrial or satellite broadcasting or the like are received in the tuner within the home server, and the received data is sent from the server to the client, for example to a PC or the like without a tuner, and the user views and listens to various television or radio programs via the display and speaker provided on the PC.
A system wherein the server is operated remotely from the client, and the television data received by the tuner within the server is received and played back on the client side via a local area network, is described in for example Patent Document 1 (1 Japanese Unexamined Patent Application Publication No. 2002-84484).
However, the configuration described in Patent Document 1 is such that the data received by the tuner within the server is stored in a storage means within the server, for example an HDD, and this storage data is provided to the client, and realizes virtual live streaming to the tuner-received data by executing similar processing as the so-called storage content within the server that is provided to the client.
The processing in the case that the client acquires specific content from the server is processing wherein a content identifier is sent from the client to the server, and the server acquires and sends the specified content based on the received identifier from the client.
For example, a content URL (Uniform Resource Locators) which the server coordinates with the content is maintained as metadata corresponding to the content, and by generating a GET method of the HTTP (Hyper Text Transfer Protocol) wherein the client has specified the content URL and sending this to the server, the server can transmit specific content to the client based on the received URL.
If the configuration is assumed to be such that the data to be received via the tuner is sent from the server to the client based on the URL specification similar to the above-described, the server sets a large number of URLs corresponding to the data for each of a large number of channels to be received via the tuner, and the client needs to send a content request specifying a URL corresponding to each channel to the server.
However, with such a URL setting configuration for each channel, if the client tries to switch channels, it becomes necessary to newly send to the server the HTTP-GET method wherein the URL corresponding to the channel after switching is set. Accordingly, between the server and client, the connection based on the URL before switching becomes invalid, and a new connection based on a new URL is set, and delivery of the streaming data of the channel after switching is performed based on the newly set connection.
Thus, in the case of URL setting configuration for each channel, it becomes necessary to perform connection settings between the server and client each time the client switches the channel, and the burden is increased on both sides. Further, interruption of communication can occur with each channel switch, and there is the problem that a smooth processing environment such as that with channel switching using a normal television remote control cannot be obtained.
Also, in an environment where multiple clients are receiving the same program from one server and multiple users are viewing and listening, there is the problem wherein the program interrupts each time the individual users switch channels.
Further, in the case of performing recording processing of the tuner-received content on the server, the client needs to issue a recording request to the server while viewing or listening to the tuner-received content. In such a case, various processing becomes necessary on the server, such as setting a so-called video capsule for recording content. It becomes necessary for the server to concurrently execute delivery processing control to the client of the content and recording processing control, but a configuration is desired wherein the client can request and process recording of the viewing or listening content to the server with arbitrary timing without influencing control of delivery content.